Method for the preparation of heterogeneous silicone rubber moldings

Abstract

A method is disclosed for preparing a heterogeneous silicone rubber molding wherein a portion of the molding is formed from a semicured silicone rubber particulate and a portion from a thermosetting silicone rubber composition. The mold is filled with the particulate and the thermosetting silicone rubber composition, then closed and pressurized and heated, forming the portions into a single body or element by curing the thermosetting silicone rubber composition at the same time that curing of the semicured silicone rubber particulate is brought to completion.

That which is claimed is: 
     
       1. Method for the preparation of heterogeneous silicone rubber moldings wherein said method comprising filling a semicured silicone rubber particulate into the cavity of a mold, then introducing a thermosetting silicone rubber composition and closing the mold, and subsequently heating this mold with the application of pressure in order to form a single body or element by curing the aforesaid thermosetting silicone rubber composition at the same time that curing of the aforesaid semicured silicone rubber particulate is brought to completion. 
     
     
       2. Method for the preparation of heterogeneous silicone rubber moldings according to claim 1 wherein the semicured silicone rubber particulate has a JIS A hardness (Shore A durometer) of zero, and a average particle size of 0.1 to 10 mm. 
     
     
       3. Method for the preparation of heterogeneous silicone rubber moldings according to claim 1 wherein the semicured silicone rubber particulate is prepared from a silicone rubber composition whose principal components are organohydrogenpolysiloxane having at least 2 silicon-bonded hydrogen atoms in each molecule and organopolysiloxane having at least 2 silicon-bonded vinyl groups in each molecule wherein the ratio of silicon-bonded hydrogen atoms in the former organohydrogenpolysiloxane to silicon-bonded vinyl groups in the latter organopolysiloxane (SiH/Si--CH═CH2) falls within the range of 0.20 to 0.95. 
     
     
       4. Method for the preparation of heterogeneous silicone rubber moldings according to claim 3 wherein the ratio of silicon-bonded hydrogen atoms in the former organohydrogenpolysiloxane to silicon-bonded vinyl groups in the latter organopolysiloxane (SiH/Si--CH═CH2) falls within the range of 0.3 to 0.6. 
     
     
       5. Method for the preparation of heterogeneous silicone rubber moldings according to claim 3 wherein the semicured silicone rubber particulate also contains organoperoxide.